Abstract
Summary: This paper describes the way in which a new pair of McCormick's Skua became established in a vacant area in a breeding colony. The pair worked out from a central point to meet neighbouring birds on the original boundaries so that these became re‐established. Within three days of settling most of the vacant area was claimed and the pair was behaving as a recognised member of the breeding group. Eggs were laid in the first season.Following comparison with other species it is proposed that the stability found in territory boundaries from year to year arises because territories becoming vacant are occupied by replacement pairs while neighbours are inhibited from encroaching on them.